FISHERY BULLETIN: VOL. 75, NO. 1 



Freeport-Galveston and Port Aransas, Tex., and 

 Cameron, La. Fish were also collected by trawling 

 in Palacios, Galveston, and Matagorda bays, Tex., 

 and Calcasieu Lake, La. Additional fish, herein- 

 after termed reef fish, were captured by angling 

 with dead shrimp bait (about 25 mm long) near an 

 oyster bar in Galveston Bay. Collection months 

 are indicated in Figure 1. 



A sample was taken from each trawl catch by 

 shoveling into a 25-liter container small portions 

 of the catch from various areas of the deck. 

 Unusually large fish were arbitrarily selected to 

 obtain older fish to develop an ageing technique. 

 Total length was measured on each croaker. Total 

 and gonad weights and girth at the origin of the 

 dorsal fin were determined for fish over a broad 

 size range during each sampling period. Scales 

 below the lateral line posterior to the pectoral fin 

 were removed from 1,123 fish, were pressed on 

 plastic slides, and were examined using a scale 

 projector. Scales were examined from small 

 numbers of croaker collected off Mississippi and 

 Fort Pierce, Fla., and in Chesapeake Bay, Va., to 

 judge whether or not the method of age deter- 

 mination proposed herein is valid throughout 

 their range in the Carolinian Province and more 

 northerly waters. The size and appearance of the 

 gonads of more than 1,700 fish were examined, 

 and ovaries were classified following Nikolsky 

 (1963) as summarized by Bagenal and Braum 

 (1971) except that the immature and resting 

 stages were combined. 



The regressions of somatic, gonad, and total 

 weights, and girth on total length were computed 

 to express the best linear or quadratic fit using the 

 Statistical Analysis System (Service 1972). Sex 

 data were pooled to compute total weight-length, 

 somatic weight-length, and girth-length re- 

 gressions, because F tests (Ostle 1963:204) 

 indicated that pooled regression lines were 

 appropriate. 



each sex began by late August, increased greatly 

 during September, reached a peak in October, 

 declined greatly by November, and was at the 

 latter level in March. Similarly, the coefficients of 

 determination (r 2 ) of the regression lines (Table 1) 

 show that gonad weight variation in each sex was 

 increasingly associated with length until October 

 and then greatly declined. Therefore, it appears 

 that peak spawning occurred in October. Fish 

 captured in the Gulf and by the reef were in all 

 stages of development during September, as were 

 trawl-caught bay fish in October (Figure 3). 

 Therefore, spawning apparently began at least by 

 late September, and some individuals finished or 

 had nearly finished spawning then. Most spawn- 

 ing occurred during October in agreement with 

 the gonad weight-length analyses, because most 

 fish captured in the Gulf were still immature in 

 September. Most fish captured near the reef and in 

 the Gulf were ripe or spent during October and 

 November. Specimens captured in the Gulf during 

 late March were in a resting stage or nearly spent, 

 so that spawning is apparently completed by late 

 March except by a few individuals. 



Croaker started to mature at about 140-170 mm 

 total length. Extrapolated x -intercepts or inflec- 

 tion points of the regressions of gonad weight on 

 total length occur in that size range for each sex 

 (Figure 2). Developing fish as small as 136 mm 

 were observed. 



Many aspects of croaker spawning appear 

 similar throughout the Carolinian Province. The 

 prolonged spawning period suggested by our data 

 is consistent with frequently reported collections 

 offish about 25-40 mm long from October to June 

 (many references including Suttkus 1955; Bear- 

 den 1964; Hansen 1969; Parker 1971; Swingle 

 1971; Christmas and Waller 1973; Hoese 1973). 

 The apparent peak of spawning after September 

 agrees with Pearson ( 1929), Hildebrand and Cable 



SPAWNING 



Spawning occurred over a protracted period 

 extending at least from September to late March, 

 but there was a distinct peak about October. The 

 regressions of gonad weight on length were not 

 significant during May, June, or July for either 

 sex. The mean gonad weight in this period was 

 0.10 g, and its 95% confidence limits were 0.09- 

 0.11 g. The regressions of gonad weight on length 

 (Figure 2) indicate that gonad development in 



TABLE 1. — Analyses for the regressions of gonad weight (Y) in 

 grams on total length (X ) in millimeters for each sex and month. 

 All regressions were significant at a = 0.0001. 



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